The present invention relates generally to clamping or clamp rings and, more particularly, to a two-piece clamp ring assembly which is particularly well suited for holding a workpiece, such as a semiconductor wafer, firmly in place against a supporting surface particularly, during the performance of processing steps.
One-piece clamp rings are used extensively within semiconductor wafer processing chambers and elsewhere for the purpose of holding a round semiconductor wafer or other such workpiece in place on a supporting surface during the performance of various processing steps. Such one-piece clamp rings generally comprise a single generally annular structure having a series of engaging lugs on the inner circumferential portion and a series of circumferentially spaced openings extending therethrough proximate the outer circumference. Typically, eight to twelve such spaced openings are employed in the one-piece clamp ring and each such opening is adapted to receive a screw, bolt or other fastener for securing the one-piece clamp ring and thus, the semiconductor wafer or other workpiece to a supporting surface with the workpiece being held in place by the lugs.
While such one-piece clamp rings are highly effective in performing the requisite holding function, such one-piece clamp rings, particularly the portion proximate to the inner circumferential surface and the lugs which engage the semiconductor wafer or other workpiece tend to erode over time due to exposure to the materials employed in performing the various semiconductor wafer processing steps. When a one-piece clamp ring has so eroded to the point where it is no longer able to provide the proper clamping force to hold the semiconductor wafers in place, it becomes necessary to replace the entire clamp ring, which involves removing all of the securing fasteners and then installing a new clamp ring which then requires torquing all of the securing fasteners, a time consuming task which increases the semiconductor wafer processing time. The replaced one-piece clamp ring is then discarded, resulting in the loss of a substantial amount of the specialized material used in forming the one piece clamp ring.
The present invention comprises a two-piece clamp ring, including a radial outer ring section or base ring which is normally secured directly to the supporting surface and a removable, radial inner ring section or securing ring which is employed for engaging and holding the semiconductor wafer or other workpiece when removably secured or assembled to the base ring. In this manner, as the securing ring, through normal use, is eroded, the securing ring, by itself, can be quickly removed and replaced without the need for replacing the entire two ring assembly, thereby saving cost and time and more effectively utilizing the specialized material used to form the rings.